1. Field of the Invention
The present invention relates to intermittent electrical contacting mechanisms used in automotive applications. The invention more particularly concerns the electrical connection between a sliding door of a vehicle and an adjacent stationary pillar of the vehicle so as to provide electrical current to devices mounted on the sliding door when the sliding door is closed, which is when the sliding door is adjacent the pillar.
2. Discussion of the Background
The present-day-consumer of automotive vehicles is conscious of quality and value. Consumers demand that amenities once reserved for luxury automobiles be included in vehicles as popular as so-called mini-vans. A mini-van is smaller than a full-sized van. The mini-van drives more like a car, but is larger than a car. Additionally, a mini-van can fit in a parking spot sized for a car. Thus, mini-vans have a large demographic appeal, especially, among parents having children. Typically, automotive manufacturers target the sale of mini-vans to such families that are thinking of replacing their car with a larger vehicle. However, this group of consumers does not want to forgo the amenities to which they became accustomed in their cars.
Most mini-vans have at least one large sliding door formed on a side of the vehicle. The sliding door slides in a direction along the length of the mini-van""s body. The large sliding door accounts for a large expanse of the vehicles body structure. In an effort to cater to the comforts that consumers are accustomed, the mini-van manufacturers needed to do something with the interior portion of the large, boring, sliding door. In a car, such a large surface area would be occupied with glass, ventilation outlets, speakers, lights, locks, or other devices. So, mini-van manufactures wired the large sliding door with electrical devices such as a lock, speakers, anti-theft alarms, air blower motors, and etc. to make the mini-van more car-like. Then the following problem developed, how to supply the sliding door with electrical current? The manufactures solved this problem by providing an interruptible electrical connection between the sliding door and a pillar of the mini-van. When the sliding door is closed, the sliding door is adjacent to and abuts the pillar. When the sliding door is closed, electrical current is supplied to the sliding door. When the sliding door is not adjacent to and abutting the pillar, the sliding door is open. In the open position, no electricity flows to the sliding door.
Manufacturers accomplished this feat by providing an electrically conductive contact plate on the pillar and electrically conductive, spring-loaded, plungers mounted on the sliding door. When the sliding door is closed, the plungers butt-up against and contact the plate thereby making an electrical connection. The spring attached to the plunger allowed the plunger to move in a direction parallel to the sliding direction of the sliding door. As such, the plunger is held in a state of compression against the contact plate so as to ensure the electrical connection while the sliding door is closed. To accommodate tolerances and manufacturing variations, the contact position for each plunger on the contact plate is made large by providing a large contact plate. The large contact plate ensures that the plunger and plate make appropriate electrical contact.
The plunger/plate device described above has one drawback while in use: it commonly fails to perform its function over an extended period of time. The failure mode is known as fretting corrosion. Fretting corrosion is an especially insidious failure mode since it is difficult to detect until it is too late. Fretting corrosion is a combination of two separate failure modes, fretting and corrosion, which when combined together form a failure mode which is much worse than the separate effects of the separate failure modes added together individually.
Fretting has been defined as two bodies in contact with each other under load forming an interface, where vibration or repeated relative motion between the two bodies occur, and the load and the relative motion of the interface must be sufficient to produce slip or deformation of the surfaces. The fretting action typically causes the formation of debris which leads to the failure of the device, since the two bodies of the device may seize and gall, or have a loss of dimensional tolerances causing a loosening of components. Typically, the amount of relative motion is imperceptible, it is very small and is often overlooked. Overtime, and generally imperceptibly, material transfer and wear occurs until at some point in time the failure occurs. In the case of the plate/plunger device, the relative motion of the sliding door jarring about relative to the pillar causes the plungers to rub against the contact plate. Over time, the plungers wear through the contact plate and thus loose electrical conductivity between the two parts; or the contact plate is not completely worn away, but the components have lost enough material so as to form loosely fitting parts which, at best, provide intermittent electrical connection when the sliding door is in a closed position.
The corrosion component of fretting corrosion is what makes this failure mode so sinister. Corrosion, on its own, has been defined as the destruction or deterioration of a material because of reaction with its environment. Corrosion typically is classified as either wet corrosion or dry corrosion. Wet corrosion occurs when a liquid having electrolytes is present with the material. Dry corrosion occurs when no liquid is present in the environment. During the corrosion process, at the atomic level, for metallic materials, the material is oxidized thus forming oxides of the material, such as iron oxide, aluminum oxide, etc. The oxides are formed and either remain on the parts, are trapped between the parts, transferred between the surfaces, or are ejected from between the parts. In this case, when the sliding door of the mini-van is opened, the surfaces of the plungers and the contact plate are exposed to environmental elements, fluids, salt, gases, and etc. When the sliding door is closed, the environmental elements are trapped between or near the metallic plunger and metallic contact plate. On its own, over time, the corrosion process can cause failure of the plunger/plate device. The failure of the device is characterized by the loss of the non-interrupted electrical connection between the plunger and the contact plate when the sliding door is in the closed position.
However, in combination, the corrosion and fretting can cause much more damage more quickly. In the corrosion process described above, when the sliding door is closed and the mini-van drives about town, the sliding door moves relative to the pillar as described above in regard to the fretting failure mode. As the plungers move relative to the contact plate, the plungers wipe away the corrosion products and leave a clean surface of material exposed so as to be introduced into the corrosion process anew. Thus, each failure mode feeds one another, the corrosion produces more material to be transferred, the fretting constantly prepares a clean uncorroded surface ready for the corrosion process.
Thus, there is a need for a device making an electrical connection between the sliding door and the pillar of the mini-van that is not susceptible to the failure mode known as fretting corrosion.
It is an object of the invention to provide a sliding contact mechanism that minimizes fretting corrosion.
It is a further object of the invention to provide a mechanism which protects the contact zones from dust and other environmental contaminants.
It is another object of the invention to provide a mechanism which compensates for door and frame tolerances.
It is still yet another object of the invention to provide a mechanism which eliminates electrical interruption during driving of the vehicle.
It is another object of the invention to provide a mechanism which reduces the size of the device to accomplish the desired function.
It is still further another object of the invention to provide a mechanism which provides for an increased number of function within the existing hardware envelope.
It is another object of the invention to provide a mechanism having a minimum number of parts, where the parts are easy to assemble to one another thus decreasing the manufacturing and assembly costs.
In one form of the invention the sliding contact mechanism includes a sliding door contact, a spring having one end connected to the sliding door contact and another end connected to the sliding door of a mini-van, and a pillar contact attached to the stationary pillar of the mini-van. The pillar contact has a shape complementary to a shape of the sliding door contact. When the sliding door is in a closed position, the sliding door is adjacent the pillar and the sliding door contact engages and is in a closed electrical connection with the pillar contact. When the sliding door is in an open position, the sliding door is not adjacent the pillar and the sliding door contact is an open electrical connection with the sliding door contact.
In yet another form the invention, the sliding contact mechanism is mounted on a mini-van. The mini-van having a chassis, a motor mounted on the chassis, a pillar attached to the chassis, a sliding door slidably attached to the chassis, a spring attached to the sliding door, a sliding door contact attached to the sliding door, and a pillar contact attached to the pillar. The pillar contact having a shape complementary to a shape of the sliding door contact. The sliding door is adjacent the pillar when the sliding door is in a closed position. In the closed position the sliding door contact engages and makes a closed electrical connection with the pillar contact. The sliding door is not adjacent the pillar when the sliding door is in an open position. In the open position, the sliding door contact makes an open electrical connection with the sliding door contact.
Thus, the invention achieves the objectives set forth above. The invention provides an interruptible electrical connection between the sliding door and the pillar which is not as susceptible to fretting corrosion as is the conventional design.